TUESDAY, July 23 (HealthDay News) -- Warning letters about illegal treatments for diabetes that could have serious health consequences have been sent to 15 companies, the U.S. Food and Drug Administration said Tuesday.

"People with chronic or incurable diseases may feel desperate and become easy prey," Gary Coody, the FDA's national health fraud coordinator, said in an agency news release. "Bogus products for diabetes are particularly troubling because there are effective options available to help manage this serious disease rather than exposing patients to unproven and risky products."

The products are sold as dietary supplements, prescription drugs and over-the-counter drugs, including homeopathic products and alternative medicines.

Consumers who use these products could put themselves at serious risk, the FDA said. The products might contain harmful ingredients or may be otherwise unsafe, the agency warned, or they may be improperly sold as over-the-counter products when they should require a prescription.

There's also the risk that people who take these illegal products may delay or discontinue effective treatments for diabetes. Without proper disease management, diabetes patients are at increased risk for serious health complications.

"Failure to follow well-established treatment plans can lead to, among other things, amputations, kidney disease, blindness and death," Coody warned.

About 26 million people in the United States have diabetes, according to the U.S. Centers for Disease Control and Prevention. These include about 7 million who are undiagnosed.

"Products that promise an easy fix might be alluring, but consumers are gambling with their health," Coody said. "In general, diabetes is a chronic disease, but it is manageable and people can lower their risk for developing complications by following treatments prescribed by health care professionals, carefully monitoring blood sugar levels and sticking to an appropriate diet and exercise program."

Some of the companies that received warning letters also sell products for other serious conditions including cancer, sexually transmitted diseases and an eye condition called macular degeneration.